In many electronic devices such as mesotubes and the like, it is necessary to place grids or other plates in precise relationship to other similar grids or plates. In a mesotube, the grids must be essentially parallel to each other and must be spaced by a precise distance to operate efficiently. The grids or plates are supported on electrodes that permit the device to function.
For example, a tungsten lower grid in a typical mesotube is to be supported on three header pins or electrodes that are perpendicular to the plane of the grid and the upper grid is to be supported on three other header pins or electrodes that also are perpendicular to that grid. The two grids are to be spaced by a precise distance, in one design by 15 to 20 mils with a tolerance of no more than approximately + or −0.1 mil. The preferred method of attaching the grids to the electrodes, as is done in many present day electronic devices using grids, is to spot weld the grid to the electrode.
An example of an arrangement utilized in the construction of mesotubes is disclosed in U.S. Patent Publication No. 20070114264 entitled “Mesotube Electrode Attachment,” which was published on May 24, 2007 to Barrett E. Cole, et al. U.S. Patent Publication No. 20070114264 is incorporated herein by reference and discloses a device for positioning a shaped element on a surface of another element mounted on a mechanism to permit welding the element to the surface. As disclosed in U.S. Patent Publication No. 20070114264, an insulating fixture mounts the device on the mechanism and positions an extension having a clamp locating end that positions a clamp for holding the shaped element in a precise position in contact with the surface during welding. The clamp is conductive and directs current from the welding to the insulating fixture and prevents insulating fixture and prevents passage of current on the shaped element beyond the clamp.
The spot weld process utilized in prior art mesotube construction arrangements such as that disclosed in U.S. Patent Publication No. 20070114264 is fairly robust and can create damage to the insulators, which can lead to a leak. Additionally, spot welding of grids to header pins in a mesotube design can lead to defects (points) on the pin, which can generate a premature breakdown in the resulting structure in the absence of UV (Ultraviolet) radiation. It is therefore desired to eliminate both of these problems.